00:01
According to our question, daily sugar consumption in america, we'll call that random variable x, is normally distributed with a mean of 22 .7 teaspoons and a standard deviation of 4 .5 teaspoons.
00:17
And for part a, we are asked what percent of people consume more than 32 teaspoons per day? this is the probability that x is more than 32.
00:30
This can be re -expressed as one minus, the probability that.
00:34
That x is at most 32.
00:39
And we can solve this using, for example, a standard normal table or software.
00:44
I'm going to use excel here to find the answer to this.
00:48
So let's try to solve this in one step in excel.
00:51
So it's 1 minus the probability that x is at most 32.
00:55
So in excel, we select a cell and we start a computation with equals.
01:00
We do 1 minus, and now we want to use the normal distribution function.
01:04
So we type norm, and we select the one that's highlighted in blue here.
01:08
We use tab to select it, and we enter 32 for the first argument, and then the mean and standard deviation of our distribution.
01:18
And for the cumulative argument, we enter true because we want the probability that x is anything up to 32.
01:26
Hit enter and we get .0194.
01:37
And for b we want, so this as a percent is 1 .94%.
01:45
For b, we want the probability or the percent of people.
01:50
Who consume more than 18 teaspoons.
01:56
So it's the same strategy as part a.
02:01
And in fact, we can just recycle the formula that we used in part a by entering 18 for the first argument in the function...